1. Field of the Invention
The invention relates to the manufacture of integrated circuits, and more particularly to a method and apparatus for cleaving a wafer into a plurality of die, and then facilitating removal of the die for utilization in hybrid electronic assemblies.
2. Description of the Prior Art
In the manufacture of integrated circuits it is conventional to form the active regions of a large number, often hundreds, of integrated circuits, while they are still in place on the wafer, typically three or more inches in diameter. When the wafer processing is over, the individual circuits or "die" must be separated and individually applied to the "hybrids" or other substrates for utilization in electronic assemblies.
The division of the wafer into individual die is frequently by cleaving. Semiconductor materials are uniform and if scribed and appropriately stressed, will start to crack at the scribe marks. The cracking will proceed predictably in a direction to relieve the stress. Thus a scribe mark, placed on a thin semiconductor which is under a bending stress applied at the scribe mark, will initiate a crack. The crack will then propagate through the thickness of the wafer, cleaving it into two parts, and in so doing, will form a generally straight and vertical edge along the die. This principle is employed in current processes.
The standard method used in the III-V semiconductor industry is to mount a thinned wafer onto adhesive tape for both scribing and cleaving. After scribing, the tape is then flexed in two orthogonal directions using a roller or passing the tape over an edge to cause die separation. The adhesive strength required for scribing and cleaving precludes the use of vacuum pick-off to remove the die from the tape. Since the preferred method, i.e., vacuum pick-off, cannot be used, a mechanical means such as tweezers are used to remove the die from the tapes. The use of tweezers leads to mechanical damage, is slow and not easily automated, and should be avoided.
Ideally, cleaving the wafer into individual die should be integrated into the existing processes with a minimum of added steps or apparatus complications. A single positional reference for the die, through scribing and cleaving is preferable.